[SPv2] Flatten property trees in PaintRecordBuilder into a single display list.

third_party/WebKit/Source/platform/graphics/paint/PropertyTreeState.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "platform/graphics/paint/PropertyTreeState.h"
 
 #include "platform/graphics/paint/GeometryMapper.h"
 
 namespace blink {
 
+const PropertyTreeState& PropertyTreeState::root() {
+  DEFINE_STATIC_LOCAL(
+      std::unique_ptr<PropertyTreeState>, root,
+      (WTF::wrapUnique(new PropertyTreeState(
+          TransformPaintPropertyNode::root(), ClipPaintPropertyNode::root(),
+          EffectPaintPropertyNode::root()))));
+  return *root;
+}
+
 bool PropertyTreeState::hasDirectCompositingReasons() const {
   switch (innermostNode()) {
     case Transform:
       return transform()->hasDirectCompositingReasons();
     case Clip:
       return clip()->hasDirectCompositingReasons();
     case Effect:
       return effect()->hasDirectCompositingReasons();
     default:
       return false;
@@ skipping 77 matching lines @@
 #if DCHECK_IS_ON()
 
 String PropertyTreeState::toTreeString() const {
   return transform()->toTreeString() + "\n" + clip()->toTreeString() + "\n" +
          effect()->toTreeString();
 }
 
 #endif
 
 }  // namespace blink